Your air flow problem is likely due to undersized duct work. An in line booster fan may help. I suggest you consider buying a register booster fan which replaces the existing register. Here is the one I bought 3 years ago on Amazon: AC Infinity AIRTAP T4 White, Register Booster Fan for 4” x 10” Register

The fan can be programmed to turn on when the air coming out of the register is above a set temperaure for heating, and below a set temperature for cooling. The latest version can be programmed with the company's app via bluetooth. The motor speed is also programmable so it can be set low for a bedroom.The nice thing about it is the fan will continue to push out air even when the furnace has turned off but the air in the duct is still warm.

I have a heating/cooling guy that is going to re-route the duct work directly from tje furnace to hopefully also push up more air. He had only given me one blower from a company that he had used on someone else's house but I saw that it didn't have very good reviews so I was looking for a better alternative. My question was also if this booster fan could be connected to the furnace so that it would only turn on when the furnace kicked in.

Yes the fan could be wired to turn on when the furnace turns on. Another method is to install a sail switch in the duct. The sail switch turnns on the fan when it detects air flow from the furnace.

If the duct will be rerouted then does the HVAC contractor still think an inline booster fan is needed?

He thought it MAY help push air up, uncertain. Old home, no return air upstairs. But he thought the booster fan would run continuously, not to my liking for an electric bill if they use alot of energy. Do they all run continuously unless wired not to?? Hense, i was looking for recommendations of good ones that is energy efficient that may actually last.

You should not install a fan which will run continously. It will waste energy, create unnecessary noise, and have a shorter life. The control of the fan is a separate item. I am suspicious of a HVAC contractor who does not know how to control an inline booster fan.